Final answer:
The use of figurative language in the poem adds depth and imagery to the scene, enhancing the reader's understanding and adding to the overall meaning.
Step-by-step explanation:
The use of figurative language in the bolded lines adds depth and imagery to the poem. By comparing the sparks to Leo, Orion, and the Pleiades, the poet creates a vivid picture of the sparks flickering and glowing in the trees. This figurative device enhances the reader's understanding of the beauty and enchantment of the scene, and adds to the overall meaning of the poem.